1. Field of the Invention
The present invention relates to an image sensor used for an image input device and in particular, to a contact type image sensor in which a plurality of semiconductor chips are mounted as a photoelectric conversion element.
2. Description of the Related Art
As one structure of an image sensor, an image reading device is disclosed in FIG. 9 in patent document 1, in which a plurality of chips are arranged with prevention for a density difference caused by a pitch error between the chips (at a boundary of the chips) from becoming conspicuous. In the drawing, reference symbols C1 and C2 denote chips (photoelectric conversion elements), Ca and Cb denote chip ends adjacent to each other, La denotes a gap distance between the ends of adjacent chips. Further, a reference symbol r denotes an image pickup element (light receiving element), P denotes a distance between the image pickup elements, P′ denotes a distance between boundary image pickup elements. Still further, in FIG. 3(c) in patent document 1, reference symbols C14 and C21 are image pickup elements located at the boundary of the chips adjacent to each other.
Moreover, in FIG. 4 in patent document 2 is disclosed an image reading device in which a plurality of optical element chips are arranged. In the drawing, a reference symbol 1 denotes an optical element chip, 2 denotes an image pickup element (light receiving element), 3 denotes an (inclined) end surface in a longitudinal direction, 3a denotes an edge on the obverse side of the chip 1, 3b denotes an edge on the reverse side (substrate side) of the chip 1, 7 denotes a substrate, and 8 denotes silver paste.    [Patent document 1] Japanese Unexamined Patent Publication No. 2003-101724    [Patent document 2] Japanese Unexamined Patent Publication No. 6-218985
In an image sensor having a plurality of chips arranged on a substrate, a distance P′ between boundary image pickup elements become longer with respect to a distance P between image pickup elements and hence in patent document 1 an average value of the output of image pickup element C14 and the output of image pickup element C21 is added as interpolation data. Because it is not actual image data which is read by the image sensor, it means that simulation (pseudo) data is produced.
At this point, in patent document 2, the rigidity of a rotating blade is enhanced and dicing is performed while inclining the rotating blade and the edge 3a on the obverse side of chip 1 is made protruded to retract the edge 3b on the reverse side, so that the distance P′ between the boundary image pickup elements can be brought close to the actual distance P between the image pickup elements on the same chip.
However, at a time of actual production with automatic mounting by a die bonder or the like, the chips need to be previously separated and mounted in consideration of the collision (contact) of chips caused by a mounting accuracy. Moreover, even if the chips can be mounted with high accuracy in themselves, the chips are mechanically mounted on an adhesive such as silver paste 8 located below, so that the chips might be changed in positions after they are mounted.
Further, at the time of bonding the chips, the adhesive is thermally cured to fix the chips. Hence, there is presented a problem that in the case of arranging many chips, after all, the chips can not be mounted with high accuracy because the position changes of chips caused by the random movement of chips due to the shrinkage of adhesive at the time of curing, can not be neglected.